Lack of gapless playback support of the Yamaha is only in the specific case of streaming from online music services with its own MusicCast app.
All other cases are ok, ie, streaming your own music files with MusicCast app or streaming online music service and your own files using a gapless playback supporting UPnP/DLNA controller app (eg BubbleUPnP, mconnect Player, etc).
Having said that, gapless playback support of the streamer itself is irrelevant if the OP is only going to be using AirPlay and Bluetooth as mentioned in the title of this thread. In that case only the player app sending the audio via AirPlay or Bluetooth determines gapless,